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104-413: The timber rattlesnake , canebrake rattlesnake , or banded rattlesnake ( Crotalus horridus ) is a species of pit viper endemic to eastern North America. Like all other pit vipers, it is venomous , with a very toxic bite. C. horridus is the only rattlesnake species in most of the populous Northeastern United States and is second only to its relatives to the west, the prairie rattlesnake , as

208-470: A Mendelian , monogenic recessive trait relative to the spotted form. Pairings of black animals have a significantly smaller litter size than other possible pairings. Between January 1996 and March 2009, Indochinese leopards were photographed at 16 sites in the Malay Peninsula in a sampling effort of more than 1000 trap nights. Of 445 photographs of melanistic leopards, 410 were taken south of

312-423: A mutation–selection balance . It is predicted that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit, "the quasispecies effect" or the "survival of the flattest". There is no suggestion that a viral quasispecies resembles

416-400: A "classical" method of determining species, such as with Linnaeus, early in evolutionary theory. However, different phenotypes are not necessarily different species (e.g. a four-winged Drosophila born to a two-winged mother is not a different species). Species named in this manner are called morphospecies . In the 1970s, Robert R. Sokal , Theodore J. Crovello and Peter Sneath proposed

520-424: A 'smallest clade' idea" (a phylogenetic species concept). Mishler and Wilkins and others concur with this approach, even though this would raise difficulties in biological nomenclature. Wilkins cited the ichthyologist Charles Tate Regan 's early 20th century remark that "a species is whatever a suitably qualified biologist chooses to call a species". Wilkins noted that the philosopher Philip Kitcher called this

624-628: A 1778 $ 20 bill from Georgia as an early example of the colonial use of the coiled rattlesnake symbol, which later became famous on the Gadsden flag , a flag that has been used by advocates of libertarianism , individualism , and small government . This species is classified as least concern on the IUCN Red List (assessed in 2007). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in

728-428: A connected series of neighbouring populations, each of which can sexually interbreed with adjacent related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing

832-546: A daughter, at the age of three, due to a rattlesnake bite she received while playing on a woodpile in the 19th century. In Pennsylvania, it is not present west of Chestnut Ridge , which is in the Laurel Highlands , nor is it present in the urban areas of the southeastern corner of the state. Thus, its range does not include Philadelphia and Pittsburgh , the two largest cities in Pennsylvania. C. horridus

936-432: A different species from its ancestors. Viruses have enormous populations, are doubtfully living since they consist of little more than a string of DNA or RNA in a protein coat, and mutate rapidly. All of these factors make conventional species concepts largely inapplicable. A viral quasispecies is a group of genotypes related by similar mutations, competing within a highly mutagenic environment, and hence governed by

1040-503: A foraging advantage during night hunting. Typically, adaptive melanism is heritable : A dominant allele , which is entirely or nearly entirely expressed in the phenotype , is responsible for the excessive amount of melanin. By contrast, adaptive melanism associated with Batesian mimicry in Zelandoperla fenestrata stoneflies is controlled by a recessive allele at the ebony locus. Adaptive melanism has been shown to occur in

1144-508: A genetic boundary suitable for defining a species concept is present. DNA barcoding has been proposed as a way to distinguish species suitable even for non-specialists to use. One of the barcodes is a region of mitochondrial DNA within the gene for cytochrome c oxidase . A database, Barcode of Life Data System , contains DNA barcode sequences from over 190,000 species. However, scientists such as Rob DeSalle have expressed concern that classical taxonomy and DNA barcoding, which they consider

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1248-443: A high-altitude adaptation, since black fur absorbs more light for warmth. The chicken breeds Silkie and Ayam Cemani commonly exhibit this trait. Ayam Cemani is an uncommon and relatively modern breed of chicken from Indonesia. They have a dominant gene that causes hyperpigmentation (Fibromelanosis), making the chicken entirely black; including feathers, beak, and internal organs. In April 2015, an extremely rare black flamingo

1352-623: A large specimen caught in Montgomery County, Alabama , which had a total length of 159 cm (62.5 in) and weighed 2.5 kg (5.5 lb). Large specimens can reportedly weigh as much as 4.5 kg (9.9 lb). The dorsal scales are keeled and arranged in 21–26 scale rows at midbody (usually 25 rows in the southern part of its geographic range, and 23 rows in the northern part). The ventral scales number 158–177 in males and 163–183 in females. Males have 20–30 subcaudal scales , while females have 15–26. The rostral scale

1456-465: A lineage should be divided into multiple chronospecies , or when populations have diverged to have enough distinct character states to be described as cladistic species. Species and higher taxa were seen from the time of Aristotle until the 18th century as categories that could be arranged in a hierarchy, the great chain of being . In the 19th century, biologists grasped that species could evolve given sufficient time. Charles Darwin 's 1859 book On

1560-492: A misnomer, need to be reconciled, as they delimit species differently. Genetic introgression mediated by endosymbionts and other vectors can further make barcodes ineffective in the identification of species. A phylogenetic or cladistic species is "the smallest aggregation of populations (sexual) or lineages (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts)". The empirical basis – observed character states – provides

1664-576: A more threatened category. The timber rattlesnake is listed as endangered in New Jersey, Ohio, Vermont, Connecticut, Massachusetts , Virginia, Indiana, New York , Illinois, and New Hampshire. In New York, timber rattlesnakes are "extirpated at 26% of historically known dens, and nearly extirpated at another 5%". Brown (1984, 1988) suggested denning populations in New York have been reduced by 50 to 75% of their historical numbers. In Massachusetts,

1768-449: A particular species, including which genus (and higher taxa) it is placed in, is a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be corroborated or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as

1872-400: A perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that

1976-491: A population in the Adirondack Mountains of New York found that the first reproduction occurs at a mean age of 9.6 years. The mean length of reproductive cycles is 4.2 years, the mean reproductive life span is 9.6 years, and the average fecundity is 7.7 offspring per litter. Nonviable offspring were found in 20% of the field litters. Most females only reproduced once. Macrogeographic differences were observed within

2080-486: A prominent symbol of American anger and resolve during the American Revolution due to its fearsome reputation. In the 18th century, European-trained doctors and scientists had little firsthand experience with or information on timber rattlesnakes, and treatment of their bites was poorly effective. The motto Nemo me impune lacesset (with the verb in the future tense ) appears above a Crotalus horridus on

2184-654: A rust-colored vertebral stripe is present. Ventrally, they are yellowish, uniform, or marked with black. Melanism is common, and some individuals are very dark, almost solid black. The tails of C. horridus are black and can be described as 'velvety.' Timber rattlesnakes are present in the eastern United States from southern Minnesota and southern New Hampshire , south to East Texas and North Florida . One hundred and fifteen rattlesnakes have been marked within Brown County State Park in Indiana , one of

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2288-400: A short way of saying that something applies to many species within a genus, but not to all. If scientists mean that something applies to all species within a genus, they use the genus name without the specific name or epithet. The names of genera and species are usually printed in italics . However, abbreviations such as "sp." should not be italicised. When a species' identity is not clear,

2392-430: A single death resulting from its bite. Considerable geographic and ontogenetic variation occurs regarding the toxicity of the venom, which can be said for many rattlesnake species. Four venom patterns have been described for this species: Type A is largely neurotoxic , and is found in various parts of the southern range. One effect of the toxin can be generalized myokymia . Type B is hemorrhagic and proteolytic , and

2496-404: A specialist may use "cf." before the epithet to indicate that confirmation is required. The abbreviations "nr." (near) or "aff." (affine) may be used when the identity is unclear but when the species appears to be similar to the species mentioned after. With the rise of online databases, codes have been devised to provide identifiers for species that are already defined, including: The naming of

2600-523: A species as groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. It has been argued that this definition is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection. Mayr's use of the adjective "potentially" has been a point of debate; some interpretations exclude unusual or artificial matings that occur only in captivity, or that involve animals capable of mating but that do not normally do so in

2704-400: A species as determined by a taxonomist. A typological species is a group of organisms in which individuals conform to certain fixed properties (a type), so that even pre-literate people often recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens (such as longer or shorter tails) would differentiate the species. This method was used as

2808-491: A species. All species definitions assume that an organism acquires its genes from one or two parents very like the "daughter" organism, but that is not what happens in HGT. There is strong evidence of HGT between very dissimilar groups of prokaryotes , and at least occasionally between dissimilar groups of eukaryotes , including some crustaceans and echinoderms . The evolutionary biologist James Mallet concludes that there

2912-685: A species. Generally the term includes the unknown element of a distinct act of creation. Many authors have argued that a simple textbook definition, following Mayr's concept, works well for most multi-celled organisms , but breaks down in several situations: Species identification is made difficult by discordance between molecular and morphological investigations; these can be categorised as two types: (i) one morphology, multiple lineages (e.g. morphological convergence , cryptic species ) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity , multiple life-cycle stages). In addition, horizontal gene transfer (HGT) makes it difficult to define

3016-528: A taxonomic decision at the discretion of cognizant specialists, is not governed by the Codes of Zoological or Botanical Nomenclature, in contrast to the PhyloCode , and contrary to what is done in several other fields, in which the definitions of technical terms, like geochronological units and geopolitical entities, are explicitly delimited. The nomenclatural codes that guide the naming of species, including

3120-517: A traditional biological species. The International Committee on Taxonomy of Viruses has since 1962 developed a universal taxonomic scheme for viruses; this has stabilised viral taxonomy. Most modern textbooks make use of Ernst Mayr 's 1942 definition, known as the Biological Species Concept as a basis for further discussion on the definition of species. It is also called a reproductive or isolation concept. This defines

3224-643: A tree looking at the squirrel and waiting for it to come down. The primary foods by genera of timber rattlesnakes were as follows: Peromyscus (33.3%), Microtus (10.9%), Tamias (qv) (10.6%), Sylvilagus (10.4%), Sigmodon (5.3%) and Sciurus (4.2%). Based on examination of the snout-to-vent length, juvenile timber rattlesnakes were found to differ slightly in dietary preferences from adult rattlesnakes, being more likely to consume smaller prey such as shrews (averaging 8 g (0.28 oz) and unable to attack subadult eastern cottontail rabbits (averaging 500–1,000 g (1.1–2.2 lb) but Peromyscus

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3328-447: A variation on the morphological species concept, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms. It differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species

3432-722: A variety of animals, including mammals such as squirrels , many cats and canids , and coral snakes . Adaptive melanism can lead to the creation of morphs , a notable example being the peppered moth , whose evolutionary history in the United Kingdom is offered as a classic instructional tool for teaching the principles of natural selection . A more replicated example of human-induced shifts in melanism has arisen from repeated selection against melanic Zelandoperla fenestrata stonefly phenotypes following widespread deforestation in New Zealand . Industrial melanism

3536-515: A variety of reasons. Viruses are a special case, driven by a balance of mutation and selection , and can be treated as quasispecies . Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics . Early taxonomists such as Linnaeus had no option but to describe what they saw: this was later formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts,

3640-400: A waiting site for prey to pass by, giving them an elevated perch from which to effectively strike their prey, which is almost entirely terrestrial rather than arboreal (even arboreal prey such as squirrels tend to be caught when they come to the ground). If the arboreal prey (squirrels) are in the trees, it was found that the snake might indicate vertical tree posture, meaning it leans up against

3744-438: Is "an entity composed of organisms which maintains its identity from other such entities through time and over space, and which has its own independent evolutionary fate and historical tendencies". This differs from the biological species concept in embodying persistence over time. Wiley and Mayden stated that they see the evolutionary species concept as "identical" to Willi Hennig 's species-as-lineages concept, and asserted that

3848-400: Is a group of sexually reproducing organisms that recognise one another as potential mates. Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms; no matter whether populations can hybridise successfully, they are still distinct cohesion species if

3952-452: Is a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring , typically by sexual reproduction . It is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity . Other ways of defining species include their karyotype , DNA sequence, morphology , behaviour, or ecological niche . In addition, paleontologists use

4056-458: Is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognise as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters. A genetic species as defined by Robert Baker and Robert Bradley is a set of genetically isolated interbreeding populations. This

4160-438: Is an evolutionary effect in insects such as the peppered moth, Biston betularia in areas subject to industrial pollution . Darker pigmented individuals are favored by natural selection , apparently because they are better camouflaged against polluted backgrounds. When pollution was later reduced, lighter forms regained the advantage and melanism became less frequent. Other explanations have been proposed, such as that

4264-584: Is another variant of pigmentation, identifiable by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic. The morbid deposition of black matter, often of a malignant character causing pigmented tumors , is called melanosis . Melanism related to the process of adaptation is called adaptive. Most commonly, dark individuals become fitter to survive and reproduce in their environment as they are better camouflaged. This makes some species less conspicuous to predators, while others, such as leopards , use it as

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4368-414: Is called speciation . Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species . Speciation depends on a measure of reproductive isolation , a reduced gene flow. This occurs most easily in allopatric speciation, where populations are separated geographically and can diverge gradually as mutations accumulate. Reproductive isolation

4472-412: Is called the specific name or the specific epithet (in botanical nomenclature , also sometimes in zoological nomenclature ). For example, Boa constrictor is one of the species of the genus Boa , with constrictor being the species' epithet. While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example,

4576-403: Is described formally, in a publication that assigns it a unique scientific name. The description typically provides means for identifying the new species, which may not be based solely on morphology (see cryptic species ), differentiating it from other previously described and related or confusable species and provides a validly published name (in botany) or an available name (in zoology) when

4680-559: Is extirpated from Michigan , Delaware , Maine and Rhode Island , and is considered close to extirpation in New Hampshire. Generally, this species is found in deciduous forests in rugged terrain. C. horridus can be found in a variety of terrestrial habitats including lowland cane thickets (thus the common name canebrake rattlesnake), high areas around swamps and river floodplains , hardwood and pine forests, mountainous areas, and rural habitats in farming areas . During

4784-404: Is found consistently in the north and in parts of the southeast. Type A + B is found in areas where the aforementioned types apparently intergrade in southwestern Arkansas and northern Louisiana . Type C venom has none of the above components and is relatively weak. The neurotoxic component of the type A venom is referred to as canebrake toxin, and is a phospholipase A 2 . It is analogous to

4888-671: Is further weakened by the existence of microspecies , groups of organisms, including many plants, with very little genetic variability, usually forming species aggregates . For example, the dandelion Taraxacum officinale and the blackberry Rubus fruticosus are aggregates with many microspecies—perhaps 400 in the case of the blackberry and over 200 in the dandelion, complicated by hybridisation , apomixis and polyploidy , making gene flow between populations difficult to determine, and their taxonomy debatable. Species complexes occur in insects such as Heliconius butterflies, vertebrates such as Hypsiboas treefrogs, and fungi such as

4992-726: Is hard or even impossible to test. Later biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, and the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: (1) agamospecies for asexual organisms (2) biospecies for reproductively isolated sexual organisms (3) ecospecies based on ecological niches (4) evolutionary species based on lineage (5) genetic species based on gene pool (6) morphospecies based on form or phenotype and (7) taxonomic species,

5096-403: Is no easy way to tell whether related geographic or temporal forms belong to the same or different species. Species gaps can be verified only locally and at a point of time. One is forced to admit that Darwin's insight is correct: any local reality or integrity of species is greatly reduced over large geographic ranges and time periods. The botanist Brent Mishler argued that the species concept

5200-420: Is normally a little taller than it is wide. In the internasal-prefrontal area there are 4–22 scales that include 2 large, triangular internasal scales that border the rostral, followed by two large, quadrangular prefrontal scales (anterior canthals) that may contact each other along the midline, or may be separated by many small scales. Between the supraocular and internasal scales, only a single canthal scale

5304-519: Is not melanism. This rare genetic disorder is characterized by the development of macules with hyperpigmentation on the lips and oral mucosa ( melanosis ), as well as benign polyps in the gastrointestinal tract. The term melanism has been used on Usenet , internet forums and blogs to mean an African-American social movement holding that dark-skinned humans are the original people from which those of other skin color originate. The term melanism has been used in this context as early as

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5408-529: Is not possible, including adult size, color pattern, the number of dorsal scale rows, and the number of ventral scales . Dundee and Rossman (1989) recognized C. h. atricaudatus , but others take a more neutral point of view. The timber rattlesnake is one of 36 species in the genus Crotalus. This genus can be distinguished from Sistrurus by the small scales atop the head, rather than nine large scales found on Sistrurus. Adults usually grow to total length of 91–152 cm (36–60 in). In Pennsylvania ,

5512-478: Is not valid, notably because gene flux decreases gradually rather than in discrete steps, which hampers objective delimitation of species. Indeed, complex and unstable patterns of gene flux have been observed in cichlid teleosts of the East African Great Lakes . Wilkins argued that "if we were being true to evolution and the consequent phylogenetic approach to taxa, we should replace it with

5616-444: Is one of North America's most dangerous snakes, due to its long fangs, impressive size, and high venom yield. This is to some degree offset by its relatively mild disposition and long brumation period. Before striking, they often perform a good deal of preliminary rattling and feinting. Cist (1845) described how he lived in western Pennsylvania for many years, and the species was quite common there, but in all that time, he heard of only

5720-505: Is present. Five to seven intersupraocular scales are seen. The number of prefoveal scales varies between two and eight. Usually, the first supralabial scale is in broad contact with the prenasal scale , although slightly to moderately separated along its posteroventral margin by the most anterior prefoveals. Dorsally , they have a pattern of dark brown or black crossbands on a yellowish-brown or grayish background. The crossbands have irregular zig-zag edges, and may be V- or M-shaped. Often

5824-586: Is similar to Mayr's Biological Species Concept, but stresses genetic rather than reproductive isolation. In the 21st century, a genetic species could be established by comparing DNA sequences. Earlier, other methods were available, such as comparing karyotypes (sets of chromosomes ) and allozymes ( enzyme variants). An evolutionarily significant unit (ESU) or "wildlife species" is a population of organisms considered distinct for purposes of conservation. In palaeontology , with only comparative anatomy (morphology) and histology from fossils as evidence,

5928-552: Is so rare in the state that it is rarely encountered by people and is considered endangered, making it illegal to harass, kill, collect, or possess. In September 2021, a five-foot long timber rattlesnake was recorded on video on a trail in the Blue Hills Reservation. Timber rattlesnakes have already been extirpated in Maine and Rhode Island and only one population remains in New Hampshire. They are protected in many of

6032-409: Is sometimes an important source of genetic variation. Viruses can transfer genes between species. Bacteria can exchange plasmids with bacteria of other species, including some apparently distantly related ones in different phylogenetic domains , making analysis of their relationships difficult, and weakening the concept of a bacterial species. Melanism Pseudomelanism, also called abundism,

6136-594: Is threatened by hybridisation, but this can be selected against once a pair of populations have incompatible alleles of the same gene, as described in the Bateson–Dobzhansky–Muller model . A different mechanism, phyletic speciation, involves one lineage gradually changing over time into a new and distinct form (a chronospecies ), without increasing the number of resultant species. Horizontal gene transfer between organisms of different species, either through hybridisation , antigenic shift , or reassortment ,

6240-479: Is used to treat envenomations from this species. The timber rattlesnake was designated the state reptile of West Virginia in 2008. That state's legislature praised "...a proud contribution by the eighth grade class at Romney Middle School , from West Virginia's oldest county, in West Virginia's oldest town, to have been instrumental in making the timber rattlesnake the state reptile..." This snake became

6344-530: The ICZN for animals and the ICN for plants, do not make rules for defining the boundaries of the species. Research can change the boundaries, also known as circumscription, based on new evidence. Species may then need to be distinguished by the boundary definitions used, and in such cases the names may be qualified with sensu stricto ("in the narrow sense") to denote usage in the exact meaning given by an author such as

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6448-552: The Kra Isthmus , where the non-melanistic morph was never photographed. These data suggest the near fixation of the dark allele in the region. The expected time to fixation of this recessive allele due to genetic drift alone ranged from about 1,100 years to about 100,000 years. Melanism in leopards has been hypothesized to be causally associated with a selective advantage for ambush. Other theories are that genes for melanism in felines may provide resistance to viral infections, or

6552-399: The fly agaric . Natural hybridisation presents a challenge to the concept of a reproductively isolated species, as fertile hybrids permit gene flow between two populations. For example, the carrion crow Corvus corone and the hooded crow Corvus cornix appear and are classified as separate species, yet they can hybridise where their geographical ranges overlap. A ring species is

6656-507: The jaguar ( Panthera onca ) of Latin America or the leopard ( Panthera pardus ) of Africa and Asia. In contrast, the scientific names of species are chosen to be unique and universal (except for some inter-code homonyms ); they are in two parts used together : the genus as in Puma , and the specific epithet as in concolor . A species is given a taxonomic name when a type specimen

6760-406: The "cynical species concept", and arguing that far from being cynical, it usefully leads to an empirical taxonomy for any given group, based on taxonomists' experience. Other biologists have gone further and argued that we should abandon species entirely, and refer to the "Least Inclusive Taxonomic Units" (LITUs), a view that would be coherent with current evolutionary theory. The species concept

6864-500: The Appalachian states, but their populations continue to decline. While C. horridus was historically abundant throughout New England , there has been a recent decline in the last known population in New Hampshire that is heading toward extinction because of genetic isolation, inbreeding, and stochastic weather events that render the population susceptible to opportunistic pathogens. Species A species ( pl. : species)

6968-626: The Origin of Species explained how species could arise by natural selection . That understanding was greatly extended in the 20th century through genetics and population ecology . Genetic variability arises from mutations and recombination , while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures . Genes can sometimes be exchanged between species by horizontal gene transfer ; new species can arise rapidly through hybridisation and polyploidy ; and species may become extinct for

7072-405: The abbreviation "sp." in the singular or "spp." (standing for species pluralis , Latin for "multiple species") in the plural in place of the specific name or epithet (e.g. Canis sp.). This commonly occurs when authors are confident that some individuals belong to a particular genus but are not sure to which exact species they belong, as is common in paleontology . Authors may also use "spp." as

7176-570: The amount of hybridisation is insufficient to completely mix their respective gene pools . A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology , genes can move freely even between distantly related bacteria, possibly extending to the whole bacterial domain. As a rule of thumb, microbiologists have assumed that members of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA–DNA hybridisation to decide if they belong to

7280-474: The biological species concept, "the several versions" of the phylogenetic species concept, and the idea that species are of the same kind as higher taxa are not suitable for biodiversity studies (with the intention of estimating the number of species accurately). They further suggested that the concept works for both asexual and sexually-reproducing species. A version of the concept is Kevin de Queiroz 's "General Lineage Concept of Species". An ecological species

7384-505: The biological species concept, a cladistic species does not rely on reproductive isolation – its criteria are independent of processes that are integral in other concepts. Therefore, it applies to asexual lineages. However, it does not always provide clear cut and intuitively satisfying boundaries between taxa, and may require multiple sources of evidence, such as more than one polymorphic locus, to give plausible results. An evolutionary species, suggested by George Gaylord Simpson in 1951,

7488-434: The body from harmful ultraviolet radiation . The same ultraviolet radiation is essential for the synthesis of vitamin D in skin, so lighter colored skin – less melanin – is an adaptation related to the prehistoric movement of humans away from equatorial regions, as there is less exposure to sunlight at higher latitudes. People from parts of Africa, South Asia , Southeast Asia , and Australia may have very dark skin, but this

7592-428: The boundaries between closely related species become unclear with hybridisation , in a species complex of hundreds of similar microspecies , and in a ring species . Also, among organisms that reproduce only asexually , the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be

7696-461: The canebrake rattlesnake, is currently considered invalid. Previously, it was recognized by Gloyd (1936) and Klauber (1936). Based on an analysis of geographic variation, Pisani et al. (1972) concluded no subspecies should be recognized. This was rejected by Conant (1975), but followed by Collins and Knight (1980). Brown and Ernst (1986) found evidence for retaining the two subspecies, but stating them apart without having more information than usual

7800-433: The concept of a chronospecies can be applied. During anagenesis (evolution, not necessarily involving branching), some palaeontologists seek to identify a sequence of species, each one derived from the phyletically extinct one before through continuous, slow and more or less uniform change. In such a time sequence, some palaeontologists assess how much change is required for a morphologically distinct form to be considered

7904-416: The concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses ) are given a two-part name , called a "binomial". The first part of a binomial is the genus to which the species belongs. The second part

8008-435: The evidence to support hypotheses about evolutionarily divergent lineages that have maintained their hereditary integrity through time and space. Molecular markers may be used to determine diagnostic genetic differences in the nuclear or mitochondrial DNA of various species. For example, in a study done on fungi , studying the nucleotide characters using cladistic species produced the most accurate results in recognising

8112-634: The few places where they can be found in the state. Its historic range includes southern Ontario and southern Quebec in Canada , but in May 2001, the Canadian Species at Risk Act listed it as extirpated in Canada. A Canadian government sponsored recovery strategy is under study to support the reintroducing of this predator of many pests to its former Canadian habitat. Many were present in some of

8216-399: The fully black color evolved over time and was thus selected for over many generations. Melanism, meaning a mutation that results in completely dark skin, does not exist in humans. In humans, the amount of melanin is determined by three dominant alleles (AABBCC), and different ethnicities have varying amounts. Melanin is the primary determinant of the degree of skin pigmentation and protects

8320-400: The jaguarundi. Sequencing of the agouti signalling peptide in the agouti gene coding region revealed a 2-base pair deletion in black domestic cats . These variants were absent in melanistic individuals of Geoffroy's cat , oncilla , pampas cat and Asian golden cat , suggesting that melanism arose independently at least four times in the cat family. Melanism in leopards is inherited as

8424-426: The melanin pigment enhances function of immune defences, or a thermal advantage from the darker coloration. Melanistic coat coloration occurs as a common polymorphism in 11 of 37 felid species and reaches high population frequency in some cases but never achieves complete fixation . The black panther , a melanistic leopard , is common in the equatorial rainforest of Malaya and the tropical rainforest on

8528-552: The most northerly distributed venomous snake in North America. No subspecies are currently recognized. The timber rattlesnake was one of the many reptile species originally described by Carl Linnaeus in the landmark 1758 10th edition of his Systema Naturae , and still bears its original name Crotalus horridus . The subspecies C. h. atricaudatus ( Latreille in Sonnini and Latreille, 1802), often referred to as

8632-413: The neurotoxins found in the venoms of several other rattlesnake species, and when present, contributes significantly to the overall toxicity. Other components found in the venom include a small basic peptide that works as a myotoxin , a fibrinogen -clotting enzyme that can produce defibrination syndrome , and a bradykinin -releasing enzyme. CroFab antivenom , while not specific for C. horridus ,

8736-483: The numerous fungi species of all the concepts studied. Versions of the phylogenetic species concept that emphasise monophyly or diagnosability may lead to splitting of existing species, for example in Bovidae , by recognising old subspecies as species, despite the fact that there are no reproductive barriers, and populations may intergrade morphologically. Others have called this approach taxonomic inflation , diluting

8840-593: The paper is accepted for publication. The type material is usually held in a permanent repository, often the research collection of a major museum or university, that allows independent verification and the means to compare specimens. Describers of new species are asked to choose names that, in the words of the International Code of Zoological Nomenclature , are "appropriate, compact, euphonious, memorable, and do not cause offence". Books and articles sometimes intentionally do not identify species fully, using

8944-674: The person who named the species, while the antonym sensu lato ("in the broad sense") denotes a wider usage, for instance including other subspecies. Other abbreviations such as "auct." ("author"), and qualifiers such as "non" ("not") may be used to further clarify the sense in which the specified authors delineated or described the species. Species are subject to change, whether by evolving into new species, exchanging genes with other species, merging with other species or by becoming extinct. The evolutionary process by which biological populations of sexually-reproducing organisms evolve to become distinct or reproductively isolated as species

9048-479: The population and may have correlated resource levels influencing growth rates and additionally human encounters could influence survival. Their prey are mainly small mammals , but may include small birds , frogs , and other small animals. Like most rattlesnakes, timber rattlesnakes are known to use chemical cues to find sites to ambush their prey and often strike their prey and track them until they can be consumed. Timber rattlesnakes are known to use fallen logs as

9152-803: The rattlesnakes between May and early June. According to Adin Ballou , when he arrived in town in 1824, snakes were still abundant, and by 1881 they were still reported in some areas of town. Since that time their habitat has been reduced to the Blue Hills south of Boston , the Berkshires in Western Massachusetts , and parts of the Connecticut River Valley , notably in the area of the Holyoke Range . The snake

9256-487: The result of misclassification leading to questions on whether there really are any ring species. The commonly used names for kinds of organisms are often ambiguous: "cat" could mean the domestic cat, Felis catus , or the cat family, Felidae . Another problem with common names is that they often vary from place to place, so that puma, cougar, catamount, panther, painter and mountain lion all mean Puma concolor in various parts of America, while "panther" may also mean

9360-586: The ring. Ring species thus present a difficulty for any species concept that relies on reproductive isolation. However, ring species are at best rare. Proposed examples include the herring gull – lesser black-backed gull complex around the North pole, the Ensatina eschscholtzii group of 19 populations of salamanders in America, and the greenish warbler in Asia, but many so-called ring species have turned out to be

9464-580: The same hibernaculum, or communal wintering den, each year. Timber rattlesnakes occupying the same hibernaculum (especially juveniles and pregnant females) have been reported to be more closely related to each other than to the rattlesnakes in neighboring dens; studies have suggested this behavior may be related to juveniles’ ability to track chemical cues from relatives. Timber rattlesnakes have also been found to leave dens multiple times in midwinter to briefly bask. Males often mate farther away from winter hibernacula than females. A lifetime reproduction study of

9568-508: The same species. This concept was narrowed in 2006 to a similarity of 98.7%. The average nucleotide identity (ANI) method quantifies genetic distance between entire genomes , using regions of about 10,000 base pairs . With enough data from genomes of one genus, algorithms can be used to categorize species, as for Pseudomonas avellanae in 2013, and for all sequenced bacteria and archaea since 2020. Observed ANI values among sequences appear to have an "ANI gap" at 85–95%, suggesting that

9672-529: The same species. When two species names are discovered to apply to the same species, the older species name is given priority and usually retained, and the newer name considered as a junior synonym, a process called synonymy . Dividing a taxon into multiple, often new, taxa is called splitting . Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognising differences or commonalities between organisms. The circumscription of taxa, considered

9776-450: The slopes of some African mountains, such as Mount Kenya . The serval also has melanistic forms in certain areas of East Africa . In the jaguarundi , coloration varies from dark brown and gray to light reddish. Melanic forms of jaguar are common in certain parts of South America . In 1938 and 1940, two melanistic bobcats were trapped alive in sub-tropical Florida . In 2003, the dominant mode of inheritance of melanism in jaguars

9880-400: The smallest size females that could produce viable eggs was 72.2 cm (28.4 in). Most adult timber rattlesnakes found measure less than 115 cm (45 in) in total length and weigh between 500 and 1,500 g (1.1 and 3.3 lb), often being towards the lower end of that range. The maximum reported total length is 189.2 cm (74.5 in) (Klauber, 1956). Holt (1924) mentions

9984-424: The snakes are active from mid-May to mid-October. Early settlers were afraid of the snake, as its population was widespread throughout the state. The town of Westborough paid 13 men two shillings per day to rid a local hill of snakes in 1680. The hill had so many rattlesnakes, it was named "Boston Hill" because the number of snakes killed rivaled the population of the young city of Boston. In Milford , men would hunt

10088-506: The species concept and making taxonomy unstable. Yet others defend this approach, considering "taxonomic inflation" pejorative and labelling the opposing view as "taxonomic conservatism"; claiming it is politically expedient to split species and recognise smaller populations at the species level, because this means they can more easily be included as endangered in the IUCN red list and can attract conservation legislation and funding. Unlike

10192-607: The summer, gravid females seem to prefer open, rocky ledges where the temperatures are higher, while males and nongravid females tend to spend more time in cooler, denser woodland with more closed forest canopy . Female timber rattlers often bask in the sun before giving birth, in open rocky areas known as "basking knolls". During the winter, timber rattlesnakes brumate in dens and limestone crevices, often together with copperheads and black rat snakes . Timber rattlesnakes exhibit high levels of philopatry to their natural hibernaculum, which means that they are likely to return to

10296-571: The thick forest areas of central and southeastern Iowa , mostly within the Mississippi , Skunk , Iowa , and Des Moines River valleys, in several places in these areas; bites from timber rattlesnakes have been widespread, especially in a localized area of Geode State Park , in southeastern Henry County , along Credit Island Park, in southern Scott County , and in the forested areas of southern Clinton County . The museum at Amana Colony, Iowa, asserts that one founding family lost their firstborn,

10400-540: The wild. It is difficult to define a species in a way that applies to all organisms. The debate about species concepts is called the species problem. The problem was recognised even in 1859, when Darwin wrote in On the Origin of Species : I was much struck how entirely vague and arbitrary is the distinction between species and varieties. He went on to write: No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of

10504-439: The yellow spots of some sub-species are called xanthophores. It appears that the fully-black phenotypes do not ever develop these xanthophores. Alpine salamanders produce a toxin from their skin, and both fully melanistic, black salamanders and spotted individuals produce the compound. Studies done that traced DNA histories have suggested that the original alpine salamander phenotype was black with some yellow spots, meaning that

10608-414: Was confirmed by performing phenotype -transmission analysis in a 116-individual captive pedigree . Melanistic animals were found to carry at least one copy of a mutant MC1R sequence allele , bearing a 15- base pair inframe deletion. Ten unrelated melanistic jaguars were either homozygous or heterozygous for this allele. A 24-base pair deletion causes the incompletely dominant allele for melanism in

10712-562: Was spotted on the Mediterranean island of Cyprus . The alpine salamander , Salamandra atra , has one subspecies ( S. atra atra ) that is completely black. The pigment comes from a specific cell called a melanophore, which produce the compound melanin. There are four other subspecies of this salamander, and they have varying levels of melanin pigmentation. The subspecies have yellow spots in different concentrations or proportions. The pigment-producing cells that contribute to

10816-512: Was the number one prey item for both young and adult rattlesnakes. Several birds, although always secondary to mammals, are also known to be hunted, mainly ground-dwelling species such as bobwhites , but also a surprising number of passerines . Prey sometimes exhibit anti-snake displays like tail-flagging, but timber rattlesnakes show no immediate or overt response to these displays. There is no rattling, striking, or other defensive behavior in response to prey anti-snake displays. Potentially, this

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